Acetylene solvent stabilizer



nited States Patent 2,907,804 ACETYLENE SOLVENT STABILIZER Calvin Charles Rolland and Robert Bird Johnson, New

Orleans, La., assignors to American CyanamidCompany, New York, N.Y., a corporation of Maine No Drawing. Application October 26, 1956 Serial No. 618,447 1 4 Claims. (Cl. 260-679) This invention relates to the purification of an acetylene-bearing gas. More particularly, it relates to inhibiting polymer precipitation in a solvent selective in its action to acetylenes.

In the manufacture of acetylene from hydrocarbons, e.g., by the partial oxidation of natural gas, the resultant acetylene-bearing gas is generally purified by treating it with a selective solvent whereby substantially all the acetylene as well as the higher acetylenes are absorbed, while the less soluble components pass ofi' in the off-gas stream. The resultant solution of acetylenes is then treated to separate acetylene from the higher acetylenes and both from the solvent, the solvent then being recycled. Various solvents have been proposed and effectively employed in this purification system, one of a the preferred being butyrolactone.

Although this purification system has been commercially employed to a considerable extent, it suffers from Resultant accumulations of polymer small slip stream of stripped solvent with water to pre cipitate polymer which can then be separated by filtration prior to recycling of the solvent. This is not wholly satisfactory because of filtration problems caused by the fine size of the polymer. In addition, the problem of polymer precipitation within the purification system is aggravated because of the possibility of introducing additional water into the solvent. It also has been proposed 'to combat this problem by adding any of various chemical agents to the solvent believed to be capable of stabilizing the solution of higher acetylenes against polymerization. Although numerous materials have been proposed, none has been found to be particularly eifective in reducing polymer formation.

There has continued to remain, therefore, a need for inhibiting the problem of polymer formation in the purification of acetylene. Particularly, there has been a continued need for reducing the frequency of shutdowns of the purification system for cleaning necessitated by the accumulation of precipitated polymer.

In accordance with this invention, these needs are met to a most unusual and unexpected degree. It now has been found that the precipitation of polymer can be greatly inhibited by incoiporating in the solvent a compound of the formula i R: in which R and R are H or alkyl radicals of L4 carbon atoms. In contrast to theprevious use of chemical addition agents which are alleged to overcome the polymerization problem by stabilizing the solution, the agents of this invention do not reduce polymerization but appear to inhibit the precipitation of solids by forming a polymer 2,907,804 Patented Oct. 6, 1959 varied. Precipitation of polymer has been considerably inhibited in a solution containing as little as 0.01% by Weight of inhibitor. Generally, the amount of inhibitor will be greater than this and may range to as high as 5% or more, although little added advantage appears to be gained by using these higher amounts. Usually, therefore, the amount of inhibitor will be less ranging from about 0.1% to about .l.0%.

To avoid a build upof soluble polymer in the solvent, a continuous slip stream of stripped solvent may be withdrawn and treated by any means which form no part of this invention to separate the polymer.

The following examples further illustrate the invention. Unless otherwise noted, all parts are by weight.

EXAMPLE 1 Table Sample No. Inhibitor Dimethylaminopropylamine- Diethylaminopropylamine- Polymer precipitation after 16 hrs Yes No Slight No No No Similar results are obtained using other inhibitors in Varying amounts in accordance with this invention. Polymer precipitation is also inhibited in a similar manner when using selective solvents other than butyrolactone.

We claim:

1. In the preparation of acetylene in which an acetylene-bearing gas is treated with butyrolactone whereby acetylene and polyacetylenes are absorbed, the method of inhibiting polymer precipitation which comprises incorporating therein from about 0.01-5.0% by weight of a compound of the formula N-CH2CH1CH:NH1

R2 in which R and R are selected from the group consisting of H and alkyl radicals of 1-4 carbon atoms.

2. A process accordingly to claim 1 in which the compound is dimethylaminopropylarnine.

3. A process according to claim 1 in which the compound is diethylaminopropylamine.

4. A process according to claim 1 in which the com pound is present in about 0.1%-1.0% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN THE PREPARATION OF ACETYLENE IN WHICH AN ACETYLENE-BEARING GAS IS TREATED WITH BUTYROLACTONE WHEREBY ACETYLENE AND POLYACETYLENE ARE ABSORBED, THE METHOD OF INHIBITING POLYMER PRECIPITATION WHICH COMPRISES INCORPORATING THEREIN FROM ABOUT 0.01-5.0% BY WEIGHT OF A COMPOUND OF THE FORMULA 